Europhys. Lett.
Volume 73, Number 1, January 2006
Page(s) 110 - 115
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 07 December 2005
Europhys. Lett., 73 (1), pp. 110-115 (2006)
DOI: 10.1209/epl/i2005-10360-3

Structural and optical properties of $\chem{BaTiO_3}$ ultrathin films

Haizhong Guo1, Lifeng Liu1, 2, Zhenghao Chen1, Shuo Ding1, Hubin Lu1, Kui-juan Jin1, Yueliang Zhou1 and Bolin Cheng1

1  Beijing National Laboratory for Condensed Matter Physics, Institute of Physics Chinese Academy of Sciences - P.O. Box 603, Beijing 100080, PRC
2  Department of Physics, Capital Normal University - Beijing 100037, PRC

received 27 June 2005; accepted in final form 2 November 2005
published online 7 December 2005

Using laser molecular beam epitaxy technique, $\chem{BaTiO_3}$ ultrathin films of 7, 12, 25, 750 monolayer (ML) thicknesses were obtained on $\chem{MgO}$ substrates. The effect of reducing the thickness of a $\chem{BaTiO_3}$ film on its structural and optical properties was investigated by Raman scattering measurement, X-ray diffraction technique, and optical transmittance spectra. In situ reflection high-energy electron diffraction and X-ray diffraction observations have revealed that the $\chem{BaTiO_3}$ films are epitaxially grown on $\chem{MgO}$ substrates from the initial stage without any other phase formation. Even in the sample of 7$\un{ML}$, Raman scattering can reveal the structural information of the film. The $\chem{BaTiO_3}$ ultrathin films have a highly c-axis-oriented tetragonal phase, and the formation of the perovskite phase is found in films as thin as 7$\un{ML}$. An increase of the energy gap and the blue shifts of Raman modes are observed with reduction of the film thickness and the possible origin was analyzed.

77.84.Dy - Niobates, titanates, tantalates, PZT ceramics, etc.
78.30.-j - Infrared and Raman spectra.
78.70.Ck - X-ray scattering.

© EDP Sciences 2005